1. Field of the Invention
The present invention generally relates to a method of manufacturing a thin film transistor and a pixel structure, in particular, to a method of manufacturing a thin film transistor having oxide channel layer and a pixel structure has the thin film transistor.
2. Description of Related Art
Generally speaking, a pixel structure in the display panel usually adopts a thin film transistor as a switch and elements (e.g., a gate, a source, a drain, and a channel layer) that form the thin film transistor are manufactured with a plurality of thin layers, respectively. Specifically, the source and the drain are usually manufactured in the same thin layer, whereas the channel layer is manufactured with another thin layer. In addition, the manufacturing of the source and the drain can be performed before or after the manufacturing of the channel layer.
Recently, an oxide semiconductor material such as IGZO (Indium Gallium Zinc Oxide) is used for manufacturing the channel layer in the thin film transistor because of the high field-effect mobility. However, the manufacturing of the channel layer by using the oxide semiconductor material, i.e., the oxide channel layer, requires overcoming certain problems. For example, when the source and the drain are formed before the channel layer, the processing gas (e.g., oxygen) for forming the oxide channel layer may oxidize the surfaces of the source and the drain. Thereby, the oxidized surfaces of the source and the drain may result in higher contact impedance between the oxide channel layer and the source/drain and reduce the device reliability of the oxide semiconductor thin film transistor.
Alternately, when the oxide channel layer is formed before the source and the drain, the step of patterning a conductive layer into the source and the drain by using an etching process may damage the oxide channel layer, thus reducing the device reliability of the oxide semiconductor thin film transistor. Therefore, the oxide semiconductor thin film transistor though can have desirable field-effect mobility, the difficulty of manufacturing the oxide semiconductor thin film transistor need be overcome.